Process and device for sterilizing tub-shaped containers

ABSTRACT

The sterilization of open-topped containers is accomplished by vaporizing a sterilizing agent in the vicinity of the container. A conveyor for supporting containers to be sterilized brings the containers in proximity to a support means upon which are supported a heater element and a nozzle. The vertically moveable support means positions the heater element either in or immediately above the open top of the container. A sterilizing agent discharged from the nozzle impinges on the heater element and undergoes instantaneous thermal decomposition. The sterilizing agent condenses on the internal surfaces of the container.

This is a division of application Ser. No. 391,246, filed June 23, 1982,now U.S. Pat. No. 4,424,189.

TECHNICAL FIELD

The present invention relates to sterilization and particularly to thedestruction of micro-organisms in containers. More specifically, thisinvention is directed to cleansing apparatus and especially to apparatusfor use in the sterilization of open-topped containers. Accordingly, thegeneral objects of the present invention are to provide novel andimproved methods and apparatus of such character.

BACKGROUND ART

While not limited thereto in its utility, the present invention isparticularly well suited for use as a sterilizing process for killingmicro-organisms in containers which are intended to receive food-stuffs.Known processes for sterilizing containers in which food stuffs are tobe packaged include UV irradiation, treatment with a mixture of steamand air and the so-called wet aseptic technique in which the interiorwall of the container is sprayed with a hydrogen peroxide mixture andsubsequently dried. Experience has shown peroxide to be a particularlyreliable sterilizing agent for killing microorganisms and containerssubjected to the wet aseptic technique may accordingly be used when along shelf life is required.

The germicidal action of peroxide depends upon the formation of freeoxygen, the free oxygen being formed during thermal decomposition andexhibiting a particularly strong sterilizing effect at the moment offormation. The efficiency of a wet aseptic process is also attributableto the liquid hydrogen peroxide which penetrates the cell coatings ofthe microorganisms.

Under the best of circumstances, i.e., with the finest nebulisation,only thirty-five percent of the internal surface of a container can bewetted by an atomized hydrogen peroxide mixture. The inability tocompletely wet the surface of the container to be treated isattributable to the fact that droplets form on the surface and unwettedareas remain between these droplets.

Since peroxide is a toxic substance, it is necessary to removesubstantially all residues of peroxide from containers treated by a wetaseptic process. The removal of the peroxide is achieved by evaporationand thus a wet aseptic process requires, subsequent to the sprayingstep, a heating step. The combined spraying and heating steps, however,do not result in absolute sterilization of the entire internal surfaceof a treated container.

DISCLOSURE OF THE INVENTION

The present invention overcomes the above-discussed and otherdeficiencies and disadvantages of the prior art by providing a reliablewet aseptic process for sterilization of the entire internal surface ofa container in a single step operation. In accordance with the inventiona sterilizing agent, preferably a hydrogen peroxide mixture, isvaporized either within the container to be sterilized or immediately infront of the container to provide free oxygen in the container, thevapor condensing on the wall of the container as a film. Thevaporization of the sterilizing agent is caused to occur in asubstantially instantaneous manner and the condensate wets the entireinternal surface of the container being sterilized. Significantlyimproved sterilization occurs because of the wetting and also becausethe instantaneous thermal decomposition of the hydrogen peroxide,results in a vapor having, because of the significant quantity of freeoxygen present, greater germicidal activity when compared to hydrogenperoxide in its liquid phase. The present invention is a one-stepprocedure in that it is unnecessary to perform any treatment stepsparticularly an evaporation step, to remove residues of hydrogenperoxide from the container.

The present invention also encompasses apparatus for use in the practiceof the above-described novel process.

BRIEF DESCRIPTION OF DRAWING

The present invention may be better understood and its numerous objectsand advantages will become apparent to those skilled in the art byreference to the accompanying drawing wherein like reference numeralsrefer to like elements in the two figures and in which;

FIG. 1 is a schematic, cross-sectional side elevation view of apparatusin accordance with a first embodiment of the invention; and

FIG. 2 is a schematic, cross-sectional side elevation view of apparatusin accordance with a second embodiment of the invention.

BEST MODE OF CARRYING OUT THE INVENTION

Referring to FIG. 1, a conveyor for transporting containers or tubs 1which are to be sterilized is indicated at 2. The conveyor 2 is providedwith plural recesses 2a in which the tubs 1, which for example may beintended to be filled with dairy products, are supported by the lipflanges provided on the tubs. A vertically movable support 3 ispositioned above conveyor 2 and supports a plurality of spray nozzles 4,the nozzles 4 being positioned so as to be centered with respect to theconveyor recesses 2a. Each of nozzles 4 is connected, via a conduit 4a,to a source of compressed air and, by a conduit 4b, to a reservoir whichcontains a mixture of hydrogen peroxide or other suitable sterilizingagent.

During the sterilization procedure the open ends of the tubs 1 areclosed by means of caps 5 which are mounted on and hermetically sealedto the nozzles 4 as indicated at 5a. Thus the caps are provided withperipheral flanges which are urged tightly against the lip flanges ofthe tubs by the descending motion of the support 3. The discharge endsof the nozzles 4 project into the chambers defined in part by the caps5.

A heating coil 6 is supported from and extends below each of the nozzles4. In the embodiment depicted in FIG. 1 the tubs to be sterilized are offrustoconical shape and thus the heating coils 6 are in the shape oftruncated cones which project into the tubs so as to be spaced apredetermined distance from the base and wall thereof. The coils 6 areconnected to a source of electric current.

As noted above, the support member 3, and thus the nozzles 4 and heatingcoils 6, are movable vertically with respect to conveyor 2, thismovement being indicated by the double headed arrow. The rate ofvertical movement of the support 3 is synchronized with the advance ofthe rows of tubs whereby the heating coils are lowered briefly intopreviously untreated tubs, the tops of the tubs are sealed by the caps 5and the sterilization treatment is performed.

With the heating coils positioned within the tubs, as shown in FIG. 1,the spray nozzles are actuated and extremely fine droplets of a hydrogenperoxide mixture are sprayed into the tubs. The spray impinges on theheating coils, which have a surface temperature of approximately 500°C., whereupon the liquid undergoes an immediate transition to the gasphase. The free oxygen thus produced has a potent germicidal action andthe vapor subsequently precipitates as a condensate film on the internalwall of the tub whereby an absolutely reliable germicidal affect isachieved. In a preferred embodiment of the invention the hydrogenperoxide mixture employed consisted of a 35% concentration of hydrogenperoxide.

An alternative technique in accordance with the invention is depicted inFIG. 2. In the process of FIG. 2 the vaporization of the sterilizingagent is effected immediately above the container to be sterilized.Thus, apparatus for use in the practice of this alternative techniqueemploys a heating coil 8 which is positioned entirely within the cap 5,the sterilizing agent being sprayed into the chamber defined by the cap.In order to prevent loss of heat, the cap is preferably provided with acovering of a suitable insulating material as shown. Additionally, inthe FIG. 2 embodiment the cap 5 is provided with a bottom plate 9provided with one or a plurality of apertures 9a, the apertures servingthe purpose of increasing the flow velocity of the vaporized sterilizingagent to the container to thereby achieve an optimum distribution of thevapor.

While preferred embodiments have been shown and described, variousmodifications and substitutions may be made thereto without departingfrom the spirit and scope of the invention. Accordingly, it is to beunderstood that the present invention has been described by way ofillustration and not limitation.

I claim:
 1. Apparatus for sterilizing open-topped containerscomprising:conveyor means for supporting containers to be sterilized,said conveyor means moving containers to be sterilized in a firstdirection along a path; nozzle means for producing an atomized spray ofa liquid delivered thereto, said nozzle means defining a spray dischargepath having an axis; cap means, said cap means being hermeticallyaffixed to said nozzle means; means for delivering a liquid sterilizingagent capable of the formation of free oxygen upon thermal decompositionto said nozzle means whereby said nozzle means will discharge anatomized spray of said sterilizing agent; heater means, said heatermeans having a heating element with a surface which is at a temperatureabove the thermal decomposition temperature of the sterilizing agent;support means for said nozzle and heater means, said support meanspositioning said heater means so that said heater means heating elementextends across said nozzle means spray discharge path and intersects theaxis thereof so that the spray discharged from said nozzle means willimpinge upon said heater means heating element surface whereby saidsterilizing agent will undergo instantaneous thermal decomposition; andmeans for moving said support means relative to said conveyor means in asecond direction which is at an angle relative to said first directionwhereby said cap means may be selectively positioned either at a firstlocation spaced from the open top of a container to be sterilized or ata second location sealing the open top of a container to be sterilized,an atomized spray of said sterilizing agent discharged from said nozzlemeans with said cap at said second location impinging upon said heatermeans heating element surface in the vicinity of a container to besterilized, the internal surface of a container thus being sterilized bythe combined effects of the free oxygen produced during theinstantaneous thermal decomposition of said atomized sterilizing agentand of the sterilizing agent which condenses on the internal surface ofa container to be sterilized.
 2. The apparatus of claim 1 wherein saidsecond direction of motion of the support means is perpendicular to saidfirst direction of motion of containers on said conveyor means.
 3. Theapparatus of claim 1 further comprising:base plate means, said baseplate means cooperating with said cap means to define a chamber, saidheater means heating element being positioned in said chamber; said baseplate means being apertured whereby the products of the thermaldecomposition of the sterilizing agent within said chamber resultingfrom impingement of said atomized sterilizing agent on said heater meansheating element surface may flow into a container to be sterilized. 4.The apparatus of claim 3 wherein said second direction of motion of thesupport means is perpendicular to said first direction of motion ofcontainers on said conveyor means.
 5. Apparatus for sterilizingopen-topped containers comprising:conveyor means for supportingcontainers to be sterilized, said conveyor means moving containers to besterilized in a first direction along a path; nozzle means for producingan atomized spray of a liquid delivered thereto; cap means, said capmeans being hermetically affixed to said nozzle means; means fordelivering a liquid sterilizing agent capable of the formation of freeoxygen upon thermal decomposition to said nozzle means whereby saidnozzle means will discharge an atomized spray of said sterilizing agent;heater means, said heater means having a heating element with a surfacewhich is at a temperature above the thermal decomposition temperature ofthe sterilizing agent, said heater means heating element being at leastpartly positioned downstream of said nozzle means in the direction oftravel of the spray discharged from said nozzle means, said heater meansheating element extending beyond said cap means in the direction oftravel of the spray discharged from said nozzle means; support means forsaid nozzle means and heater means; and means for moving said supportmeans relative to said conveyor means in a second direction which isgenerally perpendicular to said first direction whereby said cap meansmay be selectively positioned either at a first location spaced from theopen top of a container to be sterilized or at a second location sealingthe open top of a container to be sterilized, said heater means heatingelement surface being at least partly positioned within a container tobe sterilized when said cap means is in said second location whereby thespray discharged from said nozzle means will impinge upon said heatermeans heating element surface and the atomized sterilizing agent willthereupon undergo instantaneous thermal decomposition in the vicinity ofcontainer to be sterilized, the internal surfaces of a container thusbeing sterilized by the combined effects of the free oxygen producedduring thermal decomposition of the atomized sterilizing agent and thesterilizing agent which condenses on the internal surfaces of acontainer to be sterilized.
 6. The apparatus of claim 5 wherein saidnozzle means defines a spray discharge path having an axis, wherein thespray discharged from said nozzle means diverges with respect to saidaxis and wherein said support means positions said heater means suchthat said heating element at least in part is in the path of saiddiverging spray.
 7. The apparatus of claim 6 wherein said heater meansheating element is at least partly coaxial with said nozzle means spraydischarge path axis.